Process for the production of zinc and other volatile metals



Sept. 15, 1925. 1,553,646

F. THARALDSEN PROCESS FOR THE. PRODUCTION OF ZINC AND OTHER VOIJATILE METALS Filed- Sept. 25, 1922 I k. Q \V\\ IS Q 15 K- V 52 s I l I s gnowvtoz Patented Sept. 15, 1925.

UNITED STATES- PATENT orrlcs.

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PROCESS FOR THE PRODUCTION OF ZINC AND OTHER VOLLTILE METALS.

Application M September as, 1922. Serial No. 590,434.-

for the Production of. Zinc and Other Vola- Y tile Metals, of which the following is a speci-- .fication.

When producing volatile metals by distil-- lation, and specially when making zmc,it is known that the whole quantity of -metal extracted is not obtained as pure metal in a molten state. In the case of zinc, a greater or smaller part of the extracted metal is obtained in form of blue powder, which in spite of its high contents of metal, of from 90 to 95% Zn., does notright away disen gage fluid zinc at temperatures .above themelting point of zinc.

Especially in the electrothermic manufacture of zinc, with the greater dimensions of,

the distillation chambers and the condensers necessary hereto, it-has proved to be very diificult to keep the formation 'of blue powder within reasonable bounds, and no doubt it is owing to these difficulties that the electrothermic process has not attained theftechnical propagation, which.its' advantages compared withthe old mufile process should justify.

The means hitherto employedtov reduce the formation of blue powder in "the electrothermic process have chiefly consisted in a.

mechanical treatment of the powder al ready formed, either in the condenser or after the removal from same, in order to make it yield part of its zinc contents as liquid metal. However, it is obvious that such methods are imperfect and'only to be considereed as makeshift while the difiiculties presented by the formation of powder will only be really solved by avoidin as much as ossible the conditions that lea V to the said ormation.

I have now ascertained that this can be attained by effecting the. condensation of the metal vapours under the conditions de- 4 densation-by suitable cooling for instance by air or other gas. Cooled air of a convenient temperature can eventually be caused to pass through a mantle surrounding externally those surfaces of the condenser which Internally are in touch with the metal bath.

The 'tem erature in the metal bath can be measure "continuously by any suitable means and is kept constant by regulating the quantity, or the temperature, of the coolng medium. In order to obtain a constant temperature ofcondensation care must be taken that the condensation essentially takes place against the surface of the metal bath as cooling surface. To this effect the other surfaces of the condenser are kept at a temperature' above .the condensation point, which can be made by heat-insulating these parts of the condenser so well that only an 1ns1gnificant quantity of heat dissipates.

It proves to beef great importance to avoid the formation of powder that the metal bath, on which the condensation takes place shall have a clean metallic surface, and means must therefore be provided for to remove during the operation an eventual film of oxide or a thin coating of powder, which may settle here. This can be done in diflI'erent ways. A further quantity 0f molten zinc canfor instance during work be supplied to the bath from outside whereby a current sets in on the surface of the bath towards the overflow. Through this movement of the surface of the bath the skin or the coating will move towards the overflow, and a bright surface of metal appears. It is also possible to remove the coating by means ofsuitable implements which are moved across the surface of the "bath- It is understood that also other equivalent means may be used to keep the surface of the metal bright.

The annexed drawing illustrates diagrammatically a form of arrangements which can be used in carrying out the process.

Fig. 1 is a vertical section,

From the furnace chamber A the zinc vapours pass into the condensation chamber "B where they come in contact with the metal bath C at the bottom of the condenser and condense. tablished at the be inning of the process by introduction of mo ten zinc. As the condensation goes on, a cprrespgnding quantity of Fig. 2 a transverse sect1on on the line I -22ofFig.1.' I

Naturally this metal bath is es'- 'metal passes over the overflow D down into the sump E, from where it can be drawn off.

If desired, the condenser can be provided with several metal baths C and sumps E in. a row. In Fig. 1 are shown two of each. From the last metal bath the zinc vapours,

I which are now very poor in zinc, can pass out into the air through the opening G,

eventually afterhaving passed through a,

special reservoir first where the last parts of zinc are deposited as blue powder. The arrangement for cooling the metal bath consists of a plurality of fiues J extending be-- neath the metal baths and provided with inlets and outlets j, 7' respectively for the passage of cooling air therethrou h. For maintaining the temperature of t e other surfaces of the condenser above the condensation point a covering B of a suitable heat insulation material is spread over the top and sides of the condenser. H is the inlet for molten zinc to the metal bath C for charging or cleaning it. 1

It will thus be seen that the stream of vapors enters one end of the furnace and passes over the several baths of molten zinc in succession and the condensation is facilitated by reason of the surface of the bath or baths being maintained unbroken.

By not passing the zinc vapors through the body of the bath to cause it to bubble or causing the metal to drop or splash into the bath, the surface is kept substantially continuous or unbroken whether there be surface movement or not and there is much less blue powder mixed in the bath. I claim:

1. The/process of condensing zinc which comprises maintaining an unbroken surface of a molten bath of zinc with which zinc vapors contact and on which the vapors condense and maintaining the surface bright by a surface flow from one end to the other of the bath.

2. l-he process of condensin Zinc which comprises maintaining a plurahty of succes-f sive bathsof molten zinc, the surfaces of which are maintained unbroken and are contacted by the vapors of zinc and maintaining the surface of each bath bright .by a. surface flow from one end to the other thereof. 7

perature of other interior surfaces of thethe condensatlon condenser is kept above temperature.

In witness whereof I affix my signature. FILIP THARALDSEN. 

